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Objective: Currently available treatments for neuropathic pain are only modestly efficacious when assessed in randomized clinical trials and work for only some patients in the clinic. Induced-pain or gain-of-function phenotypes have been shown to predict response to analgesics (vs placebos) in patients with neuropathic pain. However, the predictive value of these phenotypes has never been studied in post-traumatic neuropathic pain., Methods: Mixed-effects models for repeated measures were used to evaluate the efficacy of pregabalin vs placebo in subgroups with induced-pain phenotypes (i.e., hyperalgesia or allodynia) in data from a recent, multinational randomized clinical trial (N = 539) that identified phenotypic subgroups through the use of a structured clinical exam., Results: The difference in mean pain score between the active and placebo groups (i.e., delta) after 15 weeks of treatment for the subgroup with hyperalgesia was -0.76 (P = 0.001), compared with 0.19 (P = 0.47) for the subgroup that did not have hyperalgesia. The treatment-by-phenotype interaction, which tests whether subgroups have statistically different treatment responses, was significant (P = 0.0067). The delta for the subgroup with allodynia was -0.31 (P = 0.22), compared with -0.30 (P = 0.22) for the subgroup that did not have allodynia (treatment-by-phenotype interaction P = 0.98)., Conclusions: These data suggest that hyperalgesia, but not allodynia, predicts response to pregabalin in patients with chronic post-traumatic neuropathic pain. This study extends the growing data supporting the utility of induced-pain phenotypes to predict response to analgesics in post-traumatic neuropathic pain. Sensory phenotyping in large, multisite trials through the use of a structured clinical exam has the potential to accelerate the development of new analgesics and improve the generalizability of clinical trial results., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objective: To determine whether the prevailing liquid chromatography and tandem mass spectroscopy assay (LC-MS/MS) assay designed to monitor buprenorphine compliance of the sublingual formulation used in the substance abuse treatment setting can be extrapolated to the transdermal formulation used in the chronic pain treatment setting, which is 1000-fold less concentrated., Design: Retrospective chart review., Subjects: Self-reported compliant patients using the transdermal or sublingual formulations of buprenorhphine. Transdermal patch application was also visually confirmed during clinic visits., Methods: Urine drug test results from a LC-MS/MS were compared between samples from transdermal and sublingual patients., Results: While all sublingual patients tested positive for at least one metabolite of buprenorphine, only 69% of the transdermal patients did so. In addition, the most abundant metabolite in the transdermal patients was buprenorphine-glucuronide, as compared with norbuprenorphine-glucuronide in sublingual patients., Conclusions: These data suggest that currently available urine drug tests for buprenorphine, including the more expensive LC-MS/MS based assays, may not be sufficiently sensitive to detect the metabolites from transdermal buprenorphine patients. This study highlights the need to evaluate the value and sensitivity of urine drug tests given the wide range of buprenorphine dosing in clinical practice. These results underscore the need for additional cost benefit analyses comparing different confirmatory drug testing techniques including many commercially available drug testing options. © 2014 Wiley Periodicals, Inc., (Wiley Periodicals, Inc.)

Objective: Neuropathic pain screening tools have shown promise in identifying common neuropathic pain characteristics that derive from diverse etiologies (e.g., diabetic peripheral neuropathy, postherpetic neuralgia). However, no prior studies have specifically assessed whether these tools are capable of discerning the underlying pain mechanisms in the vast, heterogeneous group of patients diagnosed with failed back surgery syndrome (FBSS)., Design: In this clinical observational study, two tests for neuropathic pain characteristics, the Douleur Neuropathique en 4 (DN4) and Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaires, were performed on 43 subjects with FBSS. Subjects underwent physical or neurosensory exam components of the DN4 and LANSS in the region of most severe pain (e.g., axial low back or lower extremities). DN4 and LANSS scores were correlated with clinical history and neurologic exam, pain-related quality of life questionnaires, and compared to an independent assessment of pain distribution., Results: The presence of neuropathic characteristics, determined by the DN4 (62% sensitivity, 44% specificity), LANSS (38% sensitivity, 75% specificity; cut-offs of 4 and 12, respectively), or their combination (20% sensitivity, 58% specificity) was associated with higher pain intensity as measured by the visual analog scale (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.042), modified Brief Pain Inventory-Short Form (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.082), and Neuropathic Pain Symptom Inventory (DN4 > 4, P = 0.001; LANSS ≥ 12, P = 0.001), and greater pain-related functional impairment as measured by the Roland-Morris Disability Questionnaire (DN4 > 4, P = 0.006; LANSS ≥ 12, P = 0.018). The percentage of subjects characterized as neuropathic by the DN4 and LANSS lacked concordance (67.4 vs. 25.6), and the distribution of most severe symptoms (i.e., axial vs radicular) did not correlate with subjects determined to have neuropathic pain., Conclusions: Unlike other neuropathic syndromes, the neuropathic component of FBSS is less reliably identified by the LANSS and DN4., (Wiley Periodicals, Inc.)